During the festival of Shavuot 5751 Rabbi Menachem Mendel Schneerson o.b.m. taught that there will be a fundamental difference between the way the Messiah will access new insights in Oral Torah and the way previous generations had.
Oral Torah is a body of teachings that accompanies the written text of the Torah scroll, as well as other books of scripture. Generally speaking, it is derived from a combination of two sources: (A) Torah teachings passed down orally from generation to generation designed to clarify the original intent of a written text (by definition such a clarification has to be as old as the text itself) and (B) textual interpretation meticulously carried out on the written text (in later generations) by using traditionally accepted methods.
Originally, this entire body of Torah knowledge was kept very strictly oral. A student had to commit much of his learning to memory because in many cases, it was deemed an outright sin to write down any teaching of Oral Torah. Though for the past 1,800 years or so, out of necessity, the ban on writing down teachings from Oral Torah was suspended indefinitely. However, the term "Oral Torah" to describe this body of Torah knowledge stuck - presumably, out of deference to the preferred way to transmit these teachings.
In many cases, Torah teachings transmitted orally down the line of generations are traced directly either to Moses or to later sages who either had a prophecy and/or enacted practices. In contrast, textual interpretations are usually a result of the struggles of sages in every generation to apply the Torah's teachings to the new questions of their times. Of course, to be considered valid these new "discoveries" need to fit within the Torah's framework by demonstrating consistency with the system of accepted methods of interpretation.
However, there were instances in Jewish history when new Torah insights weren't accessed in the usual way, which is by a cerebral application of interpretative methods. Rather, they were accessed through mini-revelations known as "divine inspiration" (in Hebrew ruach hakodesh). Though these mini-revelations aren't quite on the level of Biblical prophecy. Still, they are a flow of information from spiritual sources beyond the human mind. Yet, as they flow into a sage's mind they arrive garbed in traditional methods of interpretation. Essentially, the text was interpreted from Above and this interpretation is shared below with the sage along with the new message. The sage can then present them to the wider community as a properly interpreted Torah insight. The "garb" is what allows these fresh insights to participate in the give and take of Oral Torah. Otherwise, they'd be suspected as being products of fantasy.
In contrast to these interpretative approaches, the Messiah's Oral Torah will be accessed through a very different method, a new method, never used in the past. His insights in Oral Torah will flow to him prophetically. This will probably be the first time in the long stretch of Jewish history that prophecy will be used as a method to interpret the Torah. Of course in order to find it's place on the bookshelf of Oral Torah, these interpretations arrive neatly packaged in standard Torah logic - just like all the interpretations of the past. Apparently, the challenges and questions of the Messiah's generation will be so complex that only prophecy will be capable of unraveling the Torah's message unique for His times.
The Messiah's prophetic access to deep interpretative Torah begs a couple of questions:
1) Rabbi Yosef Chaim of Bagdad teaches that the Messiah will reveal a sixth book of the Torah scroll, whose proper placement will be before Genesis - shifting Genesis over to serve as the second book of the scroll. Not surprising, the topic of the newly revealed book will be about occurrences prior to the opening narrative of Genesis. (See “Od Yosef Chai”, Page 237)
Such a discovery seems to be a contribution of Written Torah rather than Oral Torah. So why is the Messiah's main Torah contribution claimed to be in the area of Oral Torah?
2) Moses already received a general sweeping overview of the Oral Torah prophetically. So why is it considered really unique for the Messiah to receive Oral Torah prophetically?
When I first read Rabbi Yosef Chaim teach that the Messiah will reveal a sixth book of the Torah scroll, I was in a deep state of shock. To me, this seemed to contradict the teaching of the Maimonides that the Written Torah is here to stay, just the way Moses originally gave it to us. One day, years later, it suddenly dawned on me during synagogue services that the "Sixth Book" is not considered a new communication of Written Torah at all, because it's not the Messiah's innovation. It's merely a part of Moses' Torah, which was already brought down and lost because of the "golden calf". The Messiah will just be reintroducing Moses' own Torah. However, his own contribution will be exclusively in the arena of Oral Torah. His Oral Torah will be fundamentally different than the Oral Torah revealed to Moses because Moses did not receive His Oral Torah as interpretations. Rather, he received it as explanations, which were part and parcel of the prophecies communicating the written text.
This can be compared to two different ways to understand the meaning of a dream. One way is from explanations that are part of the dream itself and understood by the dreamer while dreaming. Another way is from subsequent dream interpretation, for example, in a therapist's office. Moses' Oral Torah was more like the former. He received the written text along with a surrounding body of general explanation. The Messiah's Oral Torah is more like the latter, he'll interpret the Torah to find the answers for his era.
By divine design the Messiah will be a major figure in the legacy of Torah interpretation which help shape and develop the overall body of Oral Torah. As the Jewish People journey through history, the Oral Torah develops further and further. In each generation and locale, humanity faces fresh questions and challenges. These human struggles are designed by the Creator to stimulate the growth and development of the Oral Torah.
As Torah sages toil away at interpreting the Torah's encoded message designed to shed light on these questions and challenges, new Oral Torah is born into the world. Of course, what's "new" is always seminally contained within what's "old" - the way a seed contains a tree. It's just a process of bringing forth latent details already there. However, for birth to occur there needs to be a certain minimum level of prior development or the child is not yet ready.
Similarly, the long pre-messianic era of Jewish history is like a period of pregnancy. Just like in a womb, this period is relatively speaking (spiritually) dark. What takes place during this dark period, is that Oral Torah develops through questions and challenges which stimulate an abundance of newly revealed teachings and insights. Like a child in the womb, once, developed enough for birth, once a sufficient level of latent details have emerged over time, the Oral Torah is developed enough for a safe birth into the messianic era. May it be soon in our days!
Apparently, at certain stage of her development the Oral Torah requires prophetic input to mine deeper interpretations out of the written text. Possibly, this will bring the Oral Torah's interpretative tradition into full alignment with the Written Torah, which was also given prophetically; A prophecy fully mirroring a prophecy. In Kabbalah, the Written Torah is often referred to as a cosmic male figure and the Oral Torah as a cosmic female figure. The Oral Torah's growth seems to match the Kabbalistic notion of a cosmic female growing to the height of her cosmic male counterpart in a face to face relationship.